 /*
  * $Header: /cvshome/build/org.osgi.service.wireadmin/src/org/osgi/service/wireadmin/Wire.java,v 1.10 2006/07/11 00:54:10 hargrave Exp $
  *
  * Copyright (c) OSGi Alliance (2002, 2006). All Rights Reserved.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  * http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
 package org.osgi.service.wireadmin;

 import java.util.Dictionary ;

 /**
  * A connection between a Producer service and a Consumer service.
  *
  * <p>
  * A <code>Wire</code> object connects a Producer service to a Consumer service.
  * Both the Producer and Consumer services are identified by their unique
  * <code>service.pid</code> values. The Producer and Consumer services may
  * communicate with each other via <code>Wire</code> objects that connect them.
  * The Producer service may send updated values to the Consumer service by
  * calling the {@link #update} method. The Consumer service may request an
  * updated value from the Producer service by calling the {@link #poll} method.
  *
  * <p>
  * A Producer service and a Consumer service may be connected through multiple
  * <code>Wire</code> objects.
  *
  * <p>
  * Security Considerations. <code>Wire</code> objects are available to Producer
  * and Consumer services connected to a given <code>Wire</code> object and to
  * bundles which can access the <code>WireAdmin</code> service. A bundle must have
  * <code>ServicePermission[WireAdmin,GET]</code> to get the <code>WireAdmin</code>
  * service to access all <code>Wire</code> objects. A bundle registering a
  * Producer service or a Consumer service must have the appropriate
  * <code>ServicePermission[Consumer|Producer,REGISTER]</code> to register the
  * service and will be passed <code>Wire</code> objects when the service object's
  * <code>consumersConnected</code> or <code>producersConnected</code> method is
  * called.
  *
  * <p>
  * Scope. Each Wire object can have a scope set with the <code>setScope</code>
  * method. This method should be called by a Consumer service when it assumes a
  * Producer service that is composite (supports multiple information items). The
  * names in the scope must be verified by the <code>Wire</code> object before it
  * is used in communication. The semantics of the names depend on the Producer
  * service and must not be interpreted by the Wire Admin service.
  *
  * @version $Revision: 1.10 $
  */
 public interface Wire {
     /**
      * Return the state of this <code>Wire</code> object.
      *
      * <p>
      * A connected <code>Wire</code> must always be disconnected before becoming
      * invalid.
      *
      * @return <code>false</code> if this <code>Wire</code> object is invalid
      * because it has been deleted via {@link WireAdmin#deleteWire};
      * <code>true</code> otherwise.
      */
     public boolean isValid();

     /**
      * Return the connection state of this <code>Wire</code> object.
      *
      * <p>
      * A <code>Wire</code> is connected after the Wire Admin service receives
      * notification that the Producer service and the Consumer service for this
      * <code>Wire</code> object are both registered. This method will return
      * <code>true</code> prior to notifying the Producer and Consumer services via
      * calls to their respective <code>consumersConnected</code> and
      * <code>producersConnected</code> methods.
      * <p>
      * A <code>WireAdminEvent</code> of type {@link WireAdminEvent#WIRE_CONNECTED}
      * must be broadcast by the Wire Admin service when the <code>Wire</code>
      * becomes connected.
      *
      * <p>
      * A <code>Wire</code> object is disconnected when either the Consumer or
      * Producer service is unregistered or the <code>Wire</code> object is
      * deleted.
      * <p>
      * A <code>WireAdminEvent</code> of type
      * {@link WireAdminEvent#WIRE_DISCONNECTED} must be broadcast by the Wire
      * Admin service when the <code>Wire</code> becomes disconnected.
      *
      * @return <code>true</code> if both the Producer and Consumer for this
      * <code>Wire</code> object are connected to the <code>Wire</code>
      * object; <code>false</code> otherwise.
      */
     public boolean isConnected();

     /**
      * Return the list of data types understood by the Consumer service
      * connected to this <code>Wire</code> object. Note that subclasses of the
      * classes in this list are acceptable data types as well.
      *
      * <p>
      * The list is the value of the
      * {@link WireConstants#WIREADMIN_CONSUMER_FLAVORS} service property of the
      * Consumer service object connected to this object. If no such property was
      * registered or the type of the property value is not <code>Class[]</code>,
      * this method must return <code>null</code>.
      *
      * @return An array containing the list of classes understood by the
      * Consumer service or <code>null</code> if the <code>Wire</code> is not
      * connected, or the consumer did not register a
      * {@link WireConstants#WIREADMIN_CONSUMER_FLAVORS} property or the
      * value of the property is not of type <code>Class[]</code>.
      */
     public Class [] getFlavors();

     /**
      * Update the value.
      *
      * <p>
      * This methods is called by the Producer service to notify the Consumer
      * service connected to this <code>Wire</code> object of an updated value.
      * <p>
      * If the properties of this <code>Wire</code> object contain a
      * {@link WireConstants#WIREADMIN_FILTER} property, then filtering is
      * performed. If the Producer service connected to this <code>Wire</code>
      * object was registered with the service property
      * {@link WireConstants#WIREADMIN_PRODUCER_FILTERS}, the Producer service
      * will perform the filtering according to the rules specified for the
      * filter. Otherwise, this <code>Wire</code> object will perform the filtering
      * of the value.
      * <p>
      * If no filtering is done, or the filter indicates the updated value should
      * be delivered to the Consumer service, then this <code>Wire</code> object
      * must call the {@link Consumer#updated} method with the updated value. If
      * this <code>Wire</code> object is not connected, then the Consumer service
      * must not be called and the value is ignored.
      * <p>
      * If the value is an <code>Envelope</code> object, and the scope name is not
      * permitted, then the <code>Wire</code> object must ignore this call and not
      * transfer the object to the Consumer service.
      *
      * <p>
      * A <code>WireAdminEvent</code> of type {@link WireAdminEvent#WIRE_TRACE}
      * must be broadcast by the Wire Admin service after the Consumer service
      * has been successfully called.
      *
      * @param value The updated value. The value should be an instance of one of
      * the types returned by {@link #getFlavors}.
      * @see WireConstants#WIREADMIN_FILTER
      */
     public void update(Object value);

     /**
      * Poll for an updated value.
      *
      * <p>
      * This methods is normally called by the Consumer service to request an
      * updated value from the Producer service connected to this <code>Wire</code>
      * object. This <code>Wire</code> object will call the {@link Producer#polled}
      * method to obtain an updated value. If this <code>Wire</code> object is not
      * connected, then the Producer service must not be called.
      * <p>
      *
      * If this <code>Wire</code> object has a scope, then this method must return
      * an array of <code>Envelope</code> objects. The objects returned must match
      * the scope of this object. The <code>Wire</code> object must remove all
      * <code>Envelope</code> objects with a scope name that is not in the
      * <code>Wire</code> object's scope. Thus, the list of objects returned must
      * only contain <code>Envelope</code> objects with a permitted scope name. If
      * the array becomes empty, <code>null</code> must be returned.
      *
      * <p>
      * A <code>WireAdminEvent</code> of type {@link WireAdminEvent#WIRE_TRACE}
      * must be broadcast by the Wire Admin service after the Producer service
      * has been successfully called.
      *
      * @return A value whose type should be one of the types returned by
      * {@link #getFlavors},<code>Envelope[]</code>, or <code>null</code>
      * if the <code>Wire</code> object is not connected, the Producer
      * service threw an exception, or the Producer service returned a
      * value which is not an instance of one of the types returned by
      * {@link #getFlavors}.
      */
     public Object poll();

     /**
      * Return the last value sent through this <code>Wire</code> object.
      *
      * <p>
      * The returned value is the most recent, valid value passed to the
      * {@link #update} method or returned by the {@link #poll} method of this
      * object. If filtering is performed by this <code>Wire</code> object, this
      * methods returns the last value provided by the Producer service. This
      * value may be an <code>Envelope[]</code> when the Producer service uses
      * scoping. If the return value is an Envelope object (or array), it must be
      * verified that the Consumer service has the proper WirePermission to see
      * it.
      *
      * @return The last value passed though this <code>Wire</code> object or
      * <code>null</code> if no valid values have been passed or the
      * Consumer service has no permission.
      */
     public Object getLastValue();

     /**
      * Return the wire properties for this <code>Wire</code> object.
      *
      * @return The properties for this <code>Wire</code> object. The returned
      * <code>Dictionary</code> must be read only.
      */
     public Dictionary getProperties();

     /**
      * Return the calculated scope of this <code>Wire</code> object.
      *
      * The purpose of the <code>Wire</code> object's scope is to allow a Producer
      * and/or Consumer service to produce/consume different types over a single
      * <code>Wire</code> object (this was deemed necessary for efficiency
      * reasons). Both the Consumer service and the Producer service must set an
      * array of scope names (their scope) with the service registration property
      * <code>WIREADMIN_PRODUCER_SCOPE</code>, or
      * <code>WIREADMIN_CONSUMER_SCOPE</code> when they can produce multiple types.
      * If a Producer service can produce different types, it should set this
      * property to the array of scope names it can produce, the Consumer service
      * must set the array of scope names it can consume. The scope of a
      * <code>Wire</code> object is defined as the intersection of permitted scope
      * names of the Producer service and Consumer service.
      * <p>
      * If neither the Consumer, or the Producer service registers scope names
      * with its service registration, then the <code>Wire</code> object's scope
      * must be <code>null</code>.
      * <p>
      * The <code>Wire</code> object's scope must not change when a Producer or
      * Consumer services modifies its scope.
      * <p>
      * A scope name is permitted for a Producer service when the registering
      * bundle has <code>WirePermission[name,PRODUCE]</code>, and for a Consumer
      * service when the registering bundle has <code>WirePermission[name,CONSUME]</code>.
      * <p>
      * If either Consumer service or Producer service has not set a
      * <code>WIREADMIN_*_SCOPE</code> property, then the returned value must be
      * <code>null</code>.
      * <p>
      * If the scope is set, the <code>Wire</code> object must enforce the scope
      * names when <code>Envelope</code> objects are used as a parameter to update
      * or returned from the <code>poll</code> method. The <code>Wire</code> object
      * must then remove all <code>Envelope</code> objects with a scope name that
      * is not permitted.
      *
      * @return A list of permitted scope names or null if the Produce or
      * Consumer service has set no scope names.
      */
     public String [] getScope();

     /**
      * Return true if the given name is in this <code>Wire</code> object's scope.
      *
      * @param name The scope name
      * @return true if the name is listed in the permitted scope names
      */
     public boolean hasScope(String name);
 }

